Priority is claimed with respect to European Patent Application No. 00810428.3-2314 filed on May 17, 2000, in the European Patent Office, the disclosure of which is herein incorporated by reference.
The invention relates to a method and apparatus for producing a roll of printed products during a winding operation.
Methods and arrangements for producing rolls from printed products, for example newspapers and magazines, are known from prior art, for example, from the references CH-A-682 657 and EP-A-0 826 616 by the assignee of the present invention. Two winding tapes are generally used for winding the printed products into a roll. The winding tapes are supplied to the roll from a winding tape supply used as a storage element. These winding tapes can be, for example, plastic tapes. In place of several winding tapes, however, the present method can use only one winding tape, which is pulled off a winding tape supply.
To obtain a good winding quality, a constant and controlled tape tension must be maintained when winding printed products into a roll. When the winding quality is poor, the danger exists that a roll will fall apart during transport, which leads to considerable expenditure. A constant tape tension is achieved by means of a tape tension control. The rotational moment acting upon the tape depends on the filling degree of the winding tape supply. Conventionally, the roll diameter of the winding tape on the tape supply roll is scanned to determine the filling degree. A scanning lever placed against the outside of the winding tape roll is used, for example, for this purpose. However, scanners of this type are subject to malfunctions. The use of an optical scanner, for example a laser, is conceivable and suggests itself for scanning the tape roll. However, this would lead to problems due to the varied surface quality of the winding tapes.
It is an object of the invention to create a method and apparatus of the aforementioned type, which is subject to fewer malfunctions.
The above and other objects are solved by a method according to the invention for producing a roll from printed products in a winding operation. The method includes the steps of winding the printed products with winding tape onto a winding core in a manner of scaled flow, wherein the winding tape has ends and one end of the winding tape is attached to the winding core; driving a winding rug with a first drive, wherein the winding rug is arranged on the underside of the winding core and fitted against the winding core for rotating the winding core; driving a winding tape supply from which the winding tape is unwound with a second drive; and maintaining a predetermined tape tension during the winding operation. The step of maintaining the predetermined tape tension includes measuring at least one of speed and distance with measurement devices for each of the first drive and second drive to obtain measured values, computing the diameter of the winding tape supply with the measured values, and regulating a rotational moment or torque of the winding tape supply with the computed diameter of the winding tape supply to maintain the tape tension.
According to another aspect of the invention, there is provided an apparatus for producing a roll of printed products during a winding operation. The apparatus includes a winding core; a winding rug arranged on the underside of the winding core and fitted against the winding core for rotating the winding core; a winding tape supply having a diameter; at least one winding tape with two ends, wherein one end is attached to the winding core and the other end is attached to the winding tape supply, wherein the printed products are wound with the winding tape onto the winding core to form a spiral roll of printed products; a first drive driving the winding rug; a second drive driving the winding tape supply; and an apparatus for controlling tape tension for maintaining a predetermined tape tension during the winding operation.
The apparatus for controlling tape tension includes speed and distance measuring devices provided to each of the first drive and second drive for respectively providing measured values for the first drive and measured values for the second drive, wherein the measured values for the first drive and the second drive are compared during the winding operation to compute the diameter of winding tape supply and to regulate the apparatus for controlling tape tension.
With the method and apparatus according to the invention, a scanning device for the winding tape supply can be omitted. The winding tape roll diameter is determined by comparing the speed and distance measurements of the winding tape and computing the diameter. Optionally, either only the speed or distance of the winding tape can be measured. Preferably, measurements are taken on the winding rug and at the winding tape supply. As a result of comparing these measurements, the diameter of the winding tape roll is computed. The computed diameter is used to control the rotational moment of the winding tape drive and to maintain a predetermined tape tension.
According to one modification of the invention, the speed and distance measurements are measured with clock generators. Clock generators can be designed to be reliable and inexpensive. The clock generators can be used to continuously measure the speeds or distance. Furthermore, clock generators require little space and do not hinder the winding or unwinding operations. In one embodiment, a clock generator is provided on the drive wheel of the winding rug and on at least one drive wheel for the winding tape supply.
The method according to the invention is also suitable if two or more winding tapes are used. With a method of this type, several winding tape supplies and a corresponding number of winding tapes are provided. Each winding tape supply can be provided with a speed and distance measuring device.
By comparing the speeds and the distances of the different winding tape rolls, a tear in a tape can be detected at once and the necessary measures taken immediately. In particular, a tape can be fixed immediately after the tape is torn.
In case of a tear in the tape, the tape length is changed by cutting out the section with the tear. If this occurs several times, the difference in the lengths for the winding tapes can be comparably large and the danger exists that the shortest winding tape may be torn from the winding core. This occurrence can be reliably avoided with the method and apparatus of the present invention if the winding tape drive that drives the shortest winding tape is used as reference drive. Thus, when using clock generators, the clock generator showing the fastest speed is used as reference to calculate the rotational moment.
According to another modification of the method the present invention, the diameter of the winding tape roll or rolls is continuously computed during the winding operation and a paper feed is switched automatically to a another roll once a predetermined residual tape length is reached. The residual tape length depends on the location of use for the roll and is preferably defined at the respective winding station.